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Updated: Oct 1, 2025
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus MRSA
Published on: February 9, 2011
Is methicillin-susceptible Staphylococcus aureus (MSSA) CC398 a true animal-independent pathogen?
Henok Ayalew Tegegne1, Jean-Yves Madec1, Marisa Haenni1
1Unité Antibiorésistance et Virulence Bactériennes, Université Claude Bernard Lyon 1, Lyon, France.
Objectives:
Methicillin-resistant Staphylococcus aureus (MRSA) belonging to ST398 has been widely described in animals. In parallel, methicillin-susceptible (MSSA) ST398 isolates causing severe infections in humans have recently emerged as animal-independent pathogens. This study aimed at characterising MSSA CC398 from different animal species in France in comparison with MSSA CC398 genomes, mostly of human origin.
Methods:
CC398 were detected by clone-specific PCR. Antimicrobial susceptibility testing was performed using the disk diffusion method. Whole genome sequencing (WGS) was performed on 47 MRSA and MSSA isolates, of which spa-types as well as resistance and virulence genes were extracted. A maximum likelihood phylogenetic tree based on SNPs was performed on all sequenced isolates and 51 additional MRSA and MSSA data found on publicly available databases.
Results:
From 275 MSSA isolates studied, 28 (10.18%) belonged to the CC398 lineage (26 ST398 and two single-locus variants) and mainly originated from cats (n=12/44, 27.3%) and dogs (n=8/55, 14.6%). Five different spa-types were identified, t571 (n=18, 64.3%) and t1451 (n=5, 17.9%) being the most frequent ones. Out of the 28 MSSA isolates, 26 carried the scn gene, whereas 24 carried the erm(T) gene, and all were genetically similar to human isolates.
Conclusion:
This study challenges the current scientific opinion that human infections due to MSSA CC398 should only be considered an animal-independent issue.
Insights
Methicillin-susceptible Staphylococcus aureus (MSSA) CC398, previously thought to be animal-independent, is found in pets like cats and dogs. These animal-derived MSSA CC398 isolates are genetically similar to human strains, suggesting a potential animal link.
Area of Science:
- Microbiology
- Genomics
- Veterinary Medicine
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) ST398 is common in animals.
- Methicillin-susceptible Staphylococcus aureus (MSSA) ST398 is emerging as an animal-independent human pathogen.
- The animal origin and characteristics of MSSA CC398 require further investigation.
Purpose of the Study:
- To characterize MSSA CC398 isolates from various animal species in France.
- To compare animal-derived MSSA CC398 genomes with human isolates.
- To assess the genetic relatedness and potential for zoonotic transmission.
Main Methods:
- Detection of CC398 using clone-specific PCR.
- Antimicrobial susceptibility testing via disk diffusion.
- Whole genome sequencing (WGS) of 47 MRSA and MSSA isolates.
- Phylogenetic analysis using single nucleotide polymorphisms (SNPs).
Main Results:
- 28 out of 275 MSSA isolates (10.18%) belonged to the CC398 lineage.
- MSSA CC398 isolates were predominantly found in cats (27.3%) and dogs (14.6%).
- The majority of MSSA CC398 isolates carried the scn and erm(T) genes and were genetically similar to human isolates.
Conclusions:
- MSSA CC398 infections in humans may not be solely animal-independent.
- The genetic similarity suggests a potential role of animals in the epidemiology of MSSA CC398.
- Further research is needed to understand the One Health implications of MSSA CC398.
